The invention relates to a flow meter for liquid or gaseous media. The meter includes a housing having an inlet and an outlet through which the medium flows. A flow measuring device, preferably in the form of a floating body, is positioned within the housing in the flowing medium, and is shiftable or disposed for movement from an initial position to a displaced position under the influence of the lifting force produced by an increased flow of the medium through the housing. The floating body is rigidly connected via a rod with a weight body which is of ferromagnetic material, and which body is located in the field of an induction coil mounted within the housing. In this flow meter, the floating body is vertically arranged in a conical tube or passage of the housing containing the flowing medium and assumes a certain position dependent upon the influence of lifting forces generated by the flow through quantity of the medium. The lifting forces are counteracted by gravity and possibly by a spring force, or by the sum formed by both these forces. The position of the lifting body, which is dependent upon the flow through quantity, may be determined by means of the stationary housing mounted induction coil in known manner.
Such flow through quantity meters are known. An essential advantage of these meters, operating according to the floating body principle, resides in that for the measurement of liquid media they can be so dimensioned and adjusted that the gaseous component contained in the liquid, in the form of bubbles, is not included in the measured value, or only to a negligible extent. This is in contradistinction to other measuring methods using rotors.
For this reason, and because of the relatively simple mechanical construction, it was considered to use flow through meters operating according to the floating body principle in motor vehicles to determine the fuel requirements. In this type of application, additional problems occur because the measuring device is subjected to very different and fluctuating movements and position changes due to the movement of the vehicle.
Largely independent of position changes of the measuring device due to vehicle movement, is the operation of such flow through meters in which the lifting force acting upon the floating body is essentially counteracted by a spring force. A quantity measuring device of this type has also become known in which both a weight, as well as a restoring spring, act to produce the counter force. In such instances, the spring is located between the weight body and an internal collar abutment of the housing. Such an arrangement reacts particularly sensitively to fluctuations in relatively small flow through quantities, such as are to be indicated for the use of fuel in motor vehicle engines.
A further heretofore unsolved problem resides in this type of application in that the fluid flow of medium to be measured has shock waves superimposed on the measuring device, such as for example resulting from movement of the overall system or, from operation of the fuel pump, or from gas bubble formation resulting due to temperture increases. These external influences cause an undesirable deflection of the floating body and thus falsify the measurement of the flow meter.
The purpose of the invention is to so compensate the above described external influences that the measuring errors resulting therefrom are avoided, or at least reduced as far as possible.
A further problem is the difficulty encountered in making fine adjustments and/or linearizing of the measuring device during manufacture and assembly of the meter.
These and other problems are overcome by the features of the present invention as hereinafter described.